Question

What executable programs have names that are just one character long, and what do they do??

Answer 1

Any program can be an executable, and it can be named anything the user chooses, and would still function exactly the same.

PC games are often run via an executable. If you rename that executable to something else, it will still function perfectly fine.

Therefore, one character long executable programs are just executable programs that have been renamed one character long, and will function as intended.